<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 100px;
            height: 100px;
            background-color: pink;
        }
    </style>
    <script src="../js/jquery-3.3.1.min.js"></script>
</head>

<body>
    <div></div>
    <script>
        var myDiv = document.querySelector('div');
        console.log(myDiv);
        var div = $('div');
        console.log(div);
        //将dom对象转换成jquery对象
        $(myDiv);
        //将jquery对象转换成dom对象
        div[0];
        div.get(0);
    </script>
</body>

</html>